NASA scientists found evidence for life on Mars. Then they changed their minds

NASA scientists found evidence for life on Mars. Then they changed their minds

JULY 20, 1976. Gilbert Levin is on the edge of his seat. Millions of kilometres away on Mars, the Viking landers have scooped up some soil and mixed it with carbon-14-labelled nutrients. The mission's scientists have all agreed that if Levin's instruments on board the landers detect emissions of carbon-14-containing methane from the soil, then there must be life on Mars. Viking reports a positive result. Something is ingesting the nutrients, metabolising them, and then belching out gas laced with carbon-14. According to all the criteria, this should have triggered a party: it was a sign of life on Mars. But, despite the evidence, NASA said it wasn’t life.

Thirty years later, I visited Levin at his company’s headquarters in Maryland. He is more convinced than ever that his experiment worked and detected life on Mars. And he is no longer alone. Joe Miller, a cell biologist at the University of Southern California in Los Angeles, has re-analysed the data and he thinks that the emissions definitely point to life. NASA researchers are calling for a new version of Levin’s experiment to be flown to Mars. Martin Rees, the astronomer royal, calls the search for extraterrestrial life the most important scientific endeavour of our time. But have we already found it?